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Reverb vs. Delay: When to Use Each
In this article, we will answer a common question asked by music producers and mix engineers everywhere: “Should I use reverb or delay here?” This question comes up often—particularly with new producers—since both types of plug-ins serve to extend a sound after the original source has gone quiet.
In general, both reverb and delay are similar time based effects but the main difference is that a reverb emulates sound waves reflecting off surfaces to create a sense of three dimensional space. While a delay will create a copy of a signal and play it back at a desired time interval to emulate an echo effect.
Before giving you concrete examples of when to use each, I think it is important to know just a bit about how these effects work.
What does a delay plug-in do?
Delay plug-ins are simple: they capture an audio source and repeat it back one or more times shortly after the original sound. The repeats are discrete, and depending on the plug-in, they typically get quieter over time.
In the natural world, you can hear a type of delay called an “echo” in open spaces where the reflective surface is far enough away that the reflection will sound separated from the original.
If you ever go for a run at night, you might hear your footsteps reflect off a nearby building. Shouting down a well and hearing your own voice reflected back shortly thereafter is another example of an echo.
A great example of a versatile delay plug-in that can be used on vocals, synths, guitars, drums, and more is the bx_delay 2500 plug-in from Brainworx, included in the iZotope Music Production Suite 5 bundle.
What does a reverb plug-in do?
When a sound is reflected many times off of many surfaces, we get reverberation, which is a regular occurrence in our daily life. Like delay, these reflections arrive at our ears later than the original source, but the difference in time is so small that both the reflections and source are heard as a single, continuous event.
Depending on where a sound source is located in a given space, the surface materials, and the size of the space, the character of a reverberant signal can vary.
Reverb plug-ins recreate this sonic activity to give listeners the impression that the sounds they are hearing were recorded in a naturally-reverberant space, and not in a dry studio or digitally-generated environment. Luckily, plug-ins can now mimic a wide range of typical recording spaces (like a church or hall), or create entirely new ones.
Let’s go ahead and look at some examples of when to use reverb vs. delay. Keep in mind that this isn’t an exhaustive list or the only way to apply these effects, but a simple way to inspire your creativity.
1. When you have a specific space in mind, use reverb
You will hear many producers and engineers talk about “putting a sound in a space.” This is what reverb does: it situates a sound within a familiar—or not so familiar—space, setting the mood and context for a song. Are you trying to achieve the ambience of a big, industrial area? A wood cabin? A live club?
You can fiddle around with plug-in parameters to find something that brings you within range of these venues, but most reverb plug-ins come with dozens, if not hundreds, of reverb presets to get you to a starting point.
Delay won’t serve you well when re-creating a realistic jazz club or concert hall; leave that to your 'verbs.
2. If reverb is muddying the mix, use delay
Adding reverb to every track in a mix is a common mistake. Your mix will sound muddy and listeners won’t be able to hear details of instruments, making for an ear-fatiguing listen.
Reverb can also be distracting when applied carelessly to a single instrument. Without some extra attention, rogue reverb tails will wash over the mix in an awkward, synthetic way. If you’re trying to add a roomy feel to a guitar, synth, or vocal, but your reverb is making the track sound too distant and dull, try turning down the reverb—or removing it entirely—using the dry/wet control and adding a short delay instead.
You’ll get that spacious feel you’re looking for without sacrificing sonic details or emotional impact.
3. When the song is slow and open, consider using reverb
A slow, spacious song is the perfect canvas for reverb to really do it’s thing. With lots of open space and few competing elements, listeners will be able to hear long tails build up and decay naturally. And the ear candy you’ve added in laboriously, like filtering the reverb output over time and automating pitch bends, will be appreciated in full.
In fast, energetic songs, long 'verbs will usually come at the cost of clarity. The tails of hits will wash over instruments in a clumsy way and push lead elements like vocals too far back in the mix.
In these cases, you’re better off using delay in a rhythmic fashion by syncing the time parameter to the tempo of your mix, then adjusting the input until you find the right ratio of dry to wet. This brings us to our next point…
4. For improved (or completely new) grooves, use delay
Delay can do wonders when you want to enhance an existing groove or create totally new grooves out of static sounds. In fact, this is part of the underlying approach to mixing dub music.
Using a combination of reverb and delay—with an emphasis on the latter—instruments in dub tracks are equal parts music and sound-effect, creating a distinct, humid, laid-back atmosphere.
When adding delay plug-ins, I almost always sync the delay time to the tempo of the mix. This way, the repeats bounce in time with everything else and create a tighter, more cohesive feel.
By experimenting with ping pong delays, which create delays that interact in a call-and-response fashion, or by combining your delays with additional processing like distortion, you will be well on your way to generating new rhythmic ideas.
5. For a consistent feel, use reverb
Reverb creates ambience in a mix and helps bring listeners into a new sonic environment. In my experience, transporting listeners to this new location requires a degree of restraint when choosing appropriate reverb settings.
When you use lots of different reverbs with varied settings, you create a multitude of spaces, making it hard for listeners to know where they are, not to mention muddying the mix. Sticking to two or three reverbs within a unified theme (i.e. using room reverbs exclusively) will greatly help the processed elements in your mix sound cohesive, as if they naturally belong together—even if they were recorded in different spaces, or cobbled together from different sample packs.
Delay, on the other hand, will usually make the processed element stand out with a newfound air of confidence, so be mindful of your intent in both scenarios.
The use cases here shouldn’t be understood as a set of rules. They’re simply a starting point for your decision-making. Like most things in music production they are open to interpretation, and can be shaped and sculpted to fit your own style.
Another note: in many mixes, reverb and delay are used together to enhance the other’s unique characteristics. Placing one before the other, or using them in parallel, you can generate effects ranging from lush, to atmospheric, to dissonant. Go forth and make your own space in this world!